1. Field of the Invention
The present invention relates to the field of portable devices such as personal digital assistants or palmtop computer systems. More specifically, embodiments of the present invention relate to wireless communication using a portable computer system and a second (“host”) computer system.
2. Related Art
As the components required to build a computer system have reduced in size, new categories of electronic devices and computer systems have emerged. One of the new categories of computer systems is the “palmtop” computer system. A palmtop computer system is a computer that is small enough to be held in the hand of a user and can therefore be “palm-sized.” Most palmtop computer systems are used to implement various Personal Information Management (PIM) applications such as an address book, a daily organizer (calendar, datebook, etc.) and electronic notepads, to name a few. Palmtop computers with PIM software have been known as Personal Digital Assistants (PDAs). Many PDAs have a small and flat display screen associated therewith.
User convenience and device value are very important factors for portable electronic devices. Typically, portable electronic devices are employed while the user is on the run, e.g., in business meetings, on business travel, personal travel, in a vehicle, on foot, etc. Because the user may be occupied or busy while using the portable electronic device, the number of user steps or user tasks required in order to access information from an electronic device (or to store information into the electronic device) is crucial for producing a commercially successful and useful product. That is, the more difficult it is to access data from an electronic device, the less likely the user will perform those tasks to obtain the information. Likewise, the easier information is to obtain, the more likely the portable electronic device will be used to obtain that information and the more likely the portable electronic device will become a part of the user's everyday activities.
Similarly, the more useful the device, the more the device will be used and acquired. The functionality of mobile wireless devices is undergoing a transition. Mobile devices are evolving from a single application device with dedicated specific purpose communication channel (for example, a cell phone or pager), to more general-purpose devices with more flexible data communication capabilities.
More specifically, wireless technology is advancing, both in the number of options that are available for providing connectivity, and in the flexibility to provide general purpose data communication. Different technologies such as cellular technologies (e.g., CDMA, TDMA), LAN access technologies (e.g., IEEE 802.11, HomeRF) and PAN technologies (e.g., Bluetooth, IR) each address a different set of needs, and provide a different set of potential services. Mobile devices are no longer restricted to a single communication channel. Modular mobile devices allow network interfaces to be attached, allowing for unlimited communications configurations. In addition, Bluetooth technology allows a single mobile device to simultaneously access multiple piconets through a single interface.
To facilitate mobile wireless communication, several wireless modem peripheral devices are available that can be directly connected to the serial interface port of a host computer system thereby providing wireless communication to the internet. Wireless communication between two stations via the Internet requires security for the users as well as protection of any data being exchanged. More specifically, user identification and verification of authorization to access given data are both important considerations. Equally important is user protection from a replay attack whereby intercepted identification/access data is used by an attacker to gain unauthorized access to an account.
In the prior art, one method for protecting against unauthorized use of a computer system or against unauthorized access to information stored in a computer system is to use a password. However, passwords are considered by many users to be vexing and inconvenient. Passwords can lock out even an authorized user, and experience shows that passwords can be defeated by unauthorized users. In addition, while a password may prevent access to applications and information already existing on the palmtop, it will generally not prevent an unauthorized user from adding new applications and information. Thus, an unauthorized user can simply assume ownership of the palmtop and ignore the password-protected information.
In the prior art, user security is often provided by the assignment of a unique user identification number (ID) such as the manufacturers serial number (MAN) of the PDA being used. Such is the case with the Mobitex Network utilized with Palm PDAs. However, an attacker could intercept such a transaction, modify the MAN number and access a different web clipping proxy server (WCP) in order to replay the intercepted message, thereby defeating the intended user security. For other TCP/IP based wireless networks (GSM, CDPD, etc.), or wire-line networks, a MAN number may not exist and the request from a single PDA source may even be directed to other WCPservers.
A sequence number is used to thwart replay attacks for secure transactions in the prior art. Sequence numbers are stored in a given WCP server for each secure transaction. This implementation assumes that the request from one PDA will always go to the same WCP server. However, this assumption may not be valid for TCP/IP based wireless or wire-line networks because the dispatcher will not be load balanced. In such cases, the load balance could be a round robin among available servers and the storage of a sequence number in a particular server for security purposes will then result in communication failure. Actually, the assumption may be broken even in the case of multiple meta-cluster Mobitex servers, which would likewise result in failure to communicate.